write-a-skilllisted

> Source: [mattpocock/skills - productivity/writing-great-skills](https://github.com/mattpocock/skills/tree/main/skills/productivity/writing-great-skills). Kept model-invoked here (see ADR 0006); full definitions in [GLOSSARY.md](GLOSSARY.md). A skill exists to wrangle determinism out of a stochastic system. **Predictability** - the agent taking the same _process_ every run, not producing the same output - is the root virtue; every lever below serves it. **Bold terms** are defined in [`GLOSSARY.md`](GLOSSARY.md); look them up there for the full meaning. ## Invocation Two choices, trading different costs: - A **model-invoked** skill keeps a **description**, so the agent can fire it autonomously _and_ other skills can reach it (you can still type its name too). It contributes to **context load** - the description sits in the window every turn. Mechanics: omit `disable-model-invocation`, and write a model-facing description with rich trigger phrasing ("Use when the user wants..., mentions..."). - A **user-invoked** skill strips the description from the agent's reach: only you, typing its name, can invoke it - and no other skill can. Zero context load, but it spends **cognitive load**: _you_ are the index that must remember it exists. Mechanics: set `disable-model-invocation: true`; the `description` becomes human-facing - a one-line summary, trigger lists stripped. Pick model-invocation only when the agent must reach the skill on its own, or another skill must. If it only